1. Field of the Invention
The present invention relates to a process for producing polyoxymethylene. More particularly, it relates to a process for producing polyoxymethylene having high polymerization degree and high thermal stability by an advantageous industrial process.
2. Description of the Prior Arts
Polyoxymethylene have been used, as an engineering plastic, in various fields because of excellent mechanical characteristic.
However, a polyoxymethylene produced by polymerizing formaldehyde in the presence of the known catalyst has inferior thermal stability and it could not be used without a modification. Accordingly, the thermal stability of polyoxymethylene has been improved by an esterification or etherification of terminal hydroxyl groups of the polymer. In the method of improving thermal stability by modifying the terminal groups, a complicated step in which a large energy is consumed, should be employed after the polymerization and accordingly, it is not economical process.
The inventors have studied to overcome the disadvantages.